The invention relates to planar solid oxide fuel cell stacks and, more particularly, to a planar-solid oxide fuel cell stack design which increases the footprint of the stack.
It is essential from a cost reduction standpoint to increase the footprint of the solid oxide fuel cell (SOFC) stack in the plane of the cell. One approach to achieve increased in-plane footprint is to manufacture and use SOFC cells that are bigger in length and/or width in the stack. Manufacturing ceramic SOFC cells of increased dimensions and maintaining them within acceptable tolerances is fundamentally difficult. At this time, several cell manufacturers produce 4″×4″ (10 cm×10 cm) cells within acceptable dimensional tolerances. Cell manufacturers are presently attempting to produce 8″×8″ (20 cm×20 cm) cells within acceptable tolerances. Acceptable tolerances are needed to prevent cell fracture during assembly and operation of the stack. Fundamentally, from a ceramics processing standpoint further increases in size are extremely difficult and probably not cost effective. In addition, the use of larger cells raises thermal management concerns during electrochemical operation since the temperature across the cell increases with increasing in-plane cell dimension. Prior art stack designs typically use bonded glass seals and/or non-compliant interconnects and, therefore, are not easily amenable to in-plane foot print scale-up.
It is clear that the need exists for a fuel cell stack structure which reliably provides for in-plane foot print scale up, and it is the primary object of the present invention to provide such a structure.
Other objects and advantages of the invention will appear herein below.